A monograph on sleep and dream: their physiology and psychology

by Edward W. Cox

The solution most favoured by psychologists is that in sleep we lack the correcting influence of the senses. The mind, they say, having nothing wherewith to compare its own creations, necessarily accepts them as realities; it puts implicit faith in them, however monstrous, simply because they are presented to it as facts and in the same manner as facts are presented when it is awake.

I confess to great doubt if this explanation be adequate. True, that we believe the impossibilities of our dreams to be because they appear to the mind to be. But that does not explain the strange absence of perplexity and wonder when we witness (as we then verily believe) the dead alive, the distant near, and impossible things performed with ease. In our waking state, if the like dreams come into the mind at some moment of idleness, they are never mistaken for realities. Reason rejects them, and if entertained for awhile it is only as a pleasant vision. Nor is the problem solved by the suggested slumber of the reasoning faculties. These are not always asleep in dream, for often we dream that we are exercising them readily and effectively. The power of reasoning employed in dream is, however, very limited. It can exercise itself on the subject of the dream, but not upon its surroundings. It is not uncommon for the sleeper to dream that he is making a speech or preaching a sermon. The discourse is argumentative and logical. It is not merely that he dreams he is logical; he is so in fact, for the dream is often remembered after waking and no flaw is found in the argument. Nevertheless, at the moment that our reasoning faculties are constructing a strictly logical and perfectly rational discourse, they are unable to inform us—as when we are awake they would have done—that the place where we suppose the speech to be spoken, the occurrence and the occasion, are not merely fictitious but attended with the most palpable absurdities.

Looking, then, at one hemisphere only of the brain, it is difficult to infer that one or more parts of it are sleeping while the other parts are awake. May the solution of the problem be found in the fact that we have two brains? Can it be that in the condition of dream one hemisphere—that is, one mind—is awake while the other is asleep?

To answer this it is necessary to inquire what is the action of two brains working, like the two eyes, together or separately?

For the common purposes of life the two brains act in complete accord. Like the two nerves of vision, they co-ordinate. Either can act alone for the ordinary uses of existence, just as one eye will do the usual work of sight. But as we see more perfectly, extensively, and roundly with two eyes than with one—so it may be reasonably concluded that we think more truly and clearly, and feel more strongly, when the two brains act together than when one is working alone. The faculty of comparison is one of the most important of the mental powers, for it is the basis of accurate knowledge. But it is doubtful if this faculty can do its work in one brain unless co-ordinated with the same faculty in the other brain. Unlike the other mental faculties, “comparison” can exercise itself only upon two ideas. Its very purpose is to make us conscious of the resemblances and differences between any two ideas presented to it. All mental processes are successive—that is to say, no two mental actions are performed by the same mental faculty at the same instant of time. Consequently, the faculty of comparison cannot exercise itself without having before it two ideas to contrast. As one brain can present only one idea at any one moment, one brain cannot provide the materials wherewith comparison can work. The process of comparison cannot therefore be effected without the aid of the other brain. This, in healthy waking life, is done instantly, perfectly and unconsciously, by means of the power of co-ordination possessed by the two hemispheres.

Such being the action of the waking brain, does sleep present any conditions that might be explained in like manner? Suppose the state of dream to be the slumber of one hemisphere only, the other being awake. May not this solve the problem?

In dream we believe shadows to be substances, ideas to be things, incongruities to be natural, and impossibilities to be realities; and so believing, we have no sense of surprise and reason is not shocked.

Nothing of these results presents itself when we are awake. Why?

Waking, the faculty of Comparison is enabled to do its work. It compares the idea with the reality, the shadow with the substance, the dream within with the impression without, the present picture of the mind with the stored knowledge of the past. The differences being thus discovered, the mind dismisses them as being the mere visions that they are.

The mental operation is performed somewhat in this manner. Two ideas are present in the mind, which compares them and traces their resemblances and differences. The sense-borne idea being thus brought face to face, as it were, with the brain-born idea, the distinction is discovered, and the latter is relegated to the limbo of visions, the former is accepted as a reality and made the basis of action.